Cryptography is the practice and study of logical means used to achieve information confidentiality, integrity and authenticity. It covers, among other things, encryption (making some data unreadable except for those who know a given secret element, called a key), data hashing (in particular for ...

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28 views

Is it secure to use a part of the key as IV in AES?

I seen a lot of AES implementation samples wide spreaded over the Internet in almost every language I can recognize. There is one difference that I reflect to be repeated between all. Some of them ...
1
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1answer
243 views

How to make sure that the public key has not been tampered with during transit?

I understand how public key infrastructure works. There is a private and public key, and someone may use the public key to encrypt data that can only be decrypted with the private key. However ...
1
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1answer
18 views

What are common methods to verify symmetric encryption keys?

How can I be certain the same key that was used for encryption? I have an encrypted payload. I use a key and the decryption algorithm to decipher it. I understand data will be returned whether the ...
15
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8answers
5k views

Would an encryption scheme that generates an extra key to be securely stored offsite be a safe backdoor?

Let me be clear first and foremost: I do not think installing a backdoor in security algorithms is a good idea. They undermine the trust in the software and in the company that provides the service. ...
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2answers
66 views

ECDH Man-in-the-middle active attack

We have Alice and Bob. The man in the middle can manipulate(remove, add something etc.) A sent from Alice and B sent from Bob, how can he figure out what the common key K(A,B) is, without knowing ...
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1answer
299 views

Bypass SSL Certificate Pinning using SSL Vulnerablilities

I am wondering if it could be possible to sort of "bypass" the certificate pinning protection of Android or iOS using for example the POODLE SSL vulnerability. According to this blog Entry it is ...
0
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2answers
165 views

Why don't the majority of today's malware use strong cryptography?

While reading another story of botnet takedown, my wondering has reached its apogee: Why don't malware authors use cryptography (encryption + signing) provided by good libraries when their creations ...
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0answers
37 views

What is elliptic curve cryptography and how does it work? [on hold]

What is elliptic curve cryptography and how does it work? Why is is usefull and how does the computer process it?
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0answers
47 views

I have to decode this Base64 value [duplicate]

This is the Base64 value which needs to be decoded and do tell me how to do it because i also want to learn: DJkfVUyiqKVtLzSmMFOupzHtLzIfo25aVUEiVUIm
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1answer
156 views

How does the Signal Protocol, used by WhatAapp, work?

I want to understand the process of the Signal Protocol. I have google it, but I am unable to find any good article or tutorial. I want to understand the basic definition and functionality of the ...
173
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21answers
23k views

How can I explain to non-techie friends that “cryptography is good”?

After that case in which Brazilian government arrested a Facebook VP due to end-to-end encryption and no server storage of messages on WhatsApp to prove connection with a drug case, it's become pretty ...
2
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2answers
145 views

number of ciphertext-plaintext pairs needed in double encryption

So I know in single encryption you would simply require at least 1 pair of plaintext-ciphertext, to carry out an exhaustive key search; you continue trying different keys until one is found that ...
15
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4answers
80k views

CryptoWall 3 - how to prevent and how to decrypt?

My father's computer is now infected with CryptoWall 3, according to the link below. http://www.bleepingcomputer.com/virus-removal/cryptowall-ransomware-information#CryptoWall Is there a way to ...
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2answers
65 views

Asymmetric Encryption for Multiple Recipients?

Let's assume an arbitrary group of people who hold a key pair and who make their public key online accessible. Let X, A, B and C be arbitrary people from that group. Now X wants to encrypt a message ...
0
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1answer
73 views

Handling user login using asymmetric cryptography

Is it possible to implement a login protocol with asymmetric cryptography instead of the hashed password method? For example, while creating an account, the client generates a private/public key pair ...
0
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2answers
51 views

What's the best place to hide long lived encryption keys

I am considering encryption options for a new Sybase project (internal facing only, sitting in our intranet) for a client that has a security policy that requires all sensitive data to use DB ...
5
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1answer
2k views

OpenVPN Why CBC mode is recommended?

I just set up my installation of OpenVPN on my server. I am curious why the OpenVPN manual recommends CBC mode. I heard that CBC is predictable and not secure; is that true?
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0answers
121 views

Rank these ciphers in order of difficulty to attack/crack. Explain your reason? [on hold]

Caesar Cipher Vigenere Cipher Rail Fence Transposition Columnar Transposition One-Time Pad
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0answers
43 views

Bluetooth security when non-paired and/or paired [on hold]

I was reading about Bluetooth security online and, seeing the lack of papers about it (especially when compared to Wi-Fi security), I was under the impression it was secured. More specifically, my ...
14
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6answers
8k views

Is PBKDF2-based System.Cryptology.RFC2898DeriveBytes() “better” for Unicode Password hashing than traditional methods?

When is it appropriate to use RFC2898DeriveBytes versus a typical hash? Update I now understand that a KDF is typically used to create a symmetric key for possible use in encrypting a stream. I ...
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1answer
42 views

X509 / SSL certificates in practise

After learning the theory behind cryptography I'm having quite some problems understanding how SSL or X509 certificates works in practise and I simply cannot find useful information in the internet. ...
1
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2answers
182 views

encryption using two keys

The use case is analogous to accessing a safe box in a bank. There is a per-user key, unique for each user, either generated by the system or hashed from the user's password. And there is a ...
132
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5answers
123k views

Is Telegram secure?

There is a new WhatsApp-killer application called Telegram. They said that it's open source and that it has a more secure encryption. But they store all the messages in their servers and WhatsApp ...
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0answers
62 views

How Cryptographic engine affect in cryptography? [closed]

I find everything on the cryptographic engine, but I did not get a proper Information related to it
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0answers
89 views

How to break a 32 bit block cipher without key? [migrated]

From what I know Skip32 is the only 32 bit block cipher and I heard its not secure. What do I do or which tool do I use to break a 32-bit block cipher? I did search for this but all I find is attacks ...
2
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1answer
121 views

Offering a privacy scenario with PHP mcrypt library

first of all, sorry if my question is not clear, because English is not my first language. Anyway, let-me explain the concept I'm struggling to solve as the best solution. I have some guys, and they ...
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2answers
110 views

How to determine if a key is a weak key

How to do you decide that a particular key is a weak key? In the case of WEP, the weak keys seem to be those whose initialization vectors are in the form of (B + 3,255,x). Does the condition for weak ...
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0answers
49 views

Elliptic Curve Diffie-Hellman (ECDH) Key Exchange in Plain English

Can someone please explain to me what Elliptic Curve Diffie-Hellman Key Exchange is in plain English? Similar to the top answer found here: "Diffie-Hellman Key Exchange" in plain English ...
8
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3answers
906 views

How do poor-quality initialization vectors affect the security of CBC mode?

(If the consensus is that this question belongs on crypto, rather than here, please feel free to [tell me to] migrate it.) From what I have read (looking specifically at AES in Cipher Block Chaining ...
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0answers
48 views

RSA 3072 is 65,536 more difficult to factor than 2048? [migrated]

If RSA 3072 is equal to 128 bit symmetric and 2048 is equal to 112 bit symmetric then 128-112= 16 and 2^16= 65,536. In that case wouldn't this make 3072 more future proof against quantum computers or ...
1
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1answer
29 views

Possible number of collisions in a hashing function with constant message size

Jumping to conclusions from my question, can we predict possible number of collisions for a given message in a given hashing algorithm. Say I am using SHA-1 which outputs 160 characters string, and ...
-1
votes
1answer
57 views

Shouldn't multiple images always exist even in most powerful hashing algorithm?

I have a confusion in mind that since in hashing we transform a large string into a smaller fixed size string, so its unlikely that any large string has a unique hash. There had to be collisions and ...
49
votes
4answers
111k views

Is SHA1 better than md5 only because it generates a hash of 160 bits?

It is well known that SHA1 is recommended more than md5 for hashing since md5 is practically broken as lot of collisions have been found. With the birthday attack, it is possible to get a collision ...
3
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3answers
132 views

Methods for determining if a file is encypted?

I am working on a anti-ransomware project. It simply monitors the filesystem, and watches for files being created, and deleted. (also monitors for known ransomware file extensions.) Basic Operation: ...
7
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4answers
1k views

Good resources for learning cryptography and OpenSSL?

I'm a programmer and I'm working on a Single Sign-on project using SAML. I want to do all I can to make this as secure as possible. Since making a secure Single Sign-on/SAML solution requires signing ...
1
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2answers
94 views

Does unsecure delivery of keys and certs make a VPN useless?

I had to install an OpenVPN service onto a fresh, disconnected computer, but the keys and certs were delivered through an insecure computer with a highly suspect connection. Let's assume that the ...
0
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1answer
85 views

How many hashes do I need to compute to get x collisions?

I know that you need to hash about 2^(N/2) to find a collision taking into account the birthday problem. But I'm not really sure about more than one collision, I mean, collisions with different ...
1
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0answers
41 views

What is the largest cycle of RSA encryption?

Is there a maximum length of a message before it is impractical to use RSA?
42
votes
4answers
31k views

Are salted SHA-256/512 hashes still safe if the hashes and their salts are exposed?

Scenario: a database of hashed and and salted passwords, including salts for each password, is stolen by a malicious user. Passwords are 6-10 chars long and chosen by non-technical users. Can this ...
4
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0answers
89 views

Which block cipher should be used in TLS 1.2 (while keeping 1.3 in mind)?

I have been looking a bit at the various block ciphers for TLS. As everyone should (pipe dream) have migrated to TLS 1.2 by now it should be considered how to prepare for TLS 1.3, when it has been ...
13
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6answers
23k views

What does “key with length of x bits” mean?

I'd like to know what it means to say "the cryptosystem C uses keys with a length of x bits". I do not understand what the bits length means... doesn't it depend on the encoding? The same word encodes ...
20
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2answers
3k views

Why was DES with 112 bit keys (IBM) reduced to 56?

On the French wikipedia page about DES it says that the original DES algorithm from IBM used 112 bit keys. Why did they reduce this to 56 bits? Edit: ok NSA convinced IBM but today it seems like a ...
6
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2answers
663 views

Requiring 2 keys to access a content

I need to use an external service that can only be accessed by password. I don't like the idea of storing the plaintext password on the server, but AFAIK there's not much I can do. Considering this ...
1
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0answers
83 views

Why are MACs not included when defining Protocols? [migrated]

I see often in literature related to cryptographic protocols that MACs (Message Authentication Codes) are not included in protocol definitions. For example: A -> S: {TA, B}KAS S -> A: {TS, ...
7
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1answer
206 views

Encrypting individual files on OS X

I am about to go paperless, and I want to protect the documents that I scan. The use case is that I'll be scanning paper documents, encrypting each file, and storing them locally and on various backup ...
0
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0answers
3 views

How can I show RSA OAEP IND-CPA secure [migrated]

How can I show, that RSA with OAEP is IND-CPA secure by using G,H one way function?
34
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8answers
4k views

Find matching phone numbers without actually knowing them

We have a mobile app that, given two users, needs to let them see what common contacts they have based on their phone numbers. How can we do this in a cryptographically secure way and respecting the ...
23
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2answers
2k views

Why haven't (most of) the Zodiac Killer's letters been decrypted? [closed]

The Zodiac Killer (who, in fact, is not Ted Cruz) was a serial killer in the late 60's and early 70's. The twist is, he would frequently taunt the local press with cryptic letters. Four of these ...
0
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3answers
57 views

How does the meet in the middle attack work on double DES?

I am having trouble understanding the meet in the middle attack and how it works on double DES. I understand that on single DES the key length is 2^56 but why when using double DES is it 2^57? Can ...
2
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1answer
87 views

Can an attacker make in-app-purchases of my products in their app?

My iOS app needs to store a pre-shared secret. It cannot embedded within the App Bundle itself because it could be extracted by statically analysing the bundle. Apple's In-App-Purchase system allows ...